<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      div {
        width: 200px;
        height: 200px;
      }
      .one {
        background-color: olivedrab;
      }
      .two {
        background-color: transparent;
      }
      .three {
        background-color: rgba(247, 11, 164, 0.5);
      }
      .four {
        background-color: #534ec0;
      }
    </style>
  </head>
  <body>
    <div class="one"></div>
    <div class="two"></div>
    <div class="three"></div>
    <div class="four"></div>
  </body>
</html>
